Filling gaps in plywood floor.

I'm planning to apply stain and a water-based polyurethane to a plywood floor and was wondering if it's a good idea to fill in the 1/8" gaps between the pieces of plywood. My concerns are that dirt and dust will accumulate in the gaps if left unfilled.

I've read that caulking the gaps is one option. Is this true, and if so, what type of caulk is recommended and should it be applied before or after applying the polyurethane?

My initial plan was not to worry about the floor's appearance. However, after putting a lot of time and effort into building the shed, which has several custom features (i.e., vintage french doors; a 4-pane side door; custom exterior window trim and a small doghouse dormer), finishing the floor seemed like it would be a nice final touch.

I am planning to use the shed as a workshop at some point in the future after I've had time to sort through and get rid of most of the stuff that's going to be stored in the shed. When that day comes I will most likely be installing a hardwood floor.